The game is almost entirely based on the dynamically streamlined multiplayer experience activated via Steam, and is currently the most played Half-Life modification in terms of players, according to GameSpy.
Counter-Strike was developed first as a Half-Life modification. Therefore named "Half-Life: Counter-Strike." The original version was a 3rd-party Half-Life modification, but since then it has grown into a commercial mod and later advertised as separate game in itself. It still uses and runs on the Half-Life game engine and is based on its unchanged structure.